The concept of free volume available in a polymer or polymer composite has been a theoretical “construct” that enables very accurate calculation of volumetric properties of polymers and polymer composites, as temperature, pressure and mixture composition change.
However, positron annihilation experiments, requiring specialized expensive equipment, provide only an indirect free volume approximation.
In materials development, electron microscopy is currently in use. However, this process is destructive, requiring dismantling and/or removal of a sample from its environment for testing.
Thus, methods are needed to provide a non-destructive independent measurement of free volume and its change through the glass transition temperature. The ability to measure changes in free volume obtained in a continuous fashion and/or through dynamic experiments also opens new possibilities in the materials and composites and biomaterials fields.
Also needed are methods for assessing crack propagation and fatigue in polymers and polymer composites and means for repairing such cracks.
Polymers and polymer composites in use today suffer from degradation/deterioration of mechanical properties. In polymer and polymer composite structures this degradation and deterioration can lead to catastrophic failure as damage accumulates to a critical point.
Crack propagation, as a damage acceleration mechanism is a model used to follow theoretically through destructive testing of selected samples the actual damage process occurring in the field.
Ultrasound can be used to visualize damage. However, results are difficult to interpret and are generally not quantitative.
The concept of self-healing materials for repair of such cracks in polymers and polymer composites has been proposed and was demonstrated in 2001 using a polyurethane composite. This composite comprised a cross linker which was released in the damaged polymer and repaired a portion of the damage.
Currently fluorescent nanoparticles referred to as quantum dots are used as replacements for fluorescent dyes in biological and medicinal immunoassays in biology.